(a) Field of the Invention
The present disclosure relates to a transflective liquid crystal display (LCD) and a manufacturing method thereof.
(b) Description of Related Art
LCDs are classified into a transmissive LCD and a reflective LCD according to the light source. The transmissive LCD has a backlight as the light source, while the reflective LCD uses external light as the light source.
A transflective LCD which uses both a backlight and external light as the light source is also under development. The transflective LCD has merits of both the transmissive LCD and the reflective LCD. The merits of the reflective LCD are low power consumption and good visibility in a bright environment, and merits of the transmissive LCD are good visibility in a dark environment such as an indoor situation. Accordingly, the transflective LCD can be used regardless of brightness of the environment, and is useful for a mobile display due to its low power consumption.
FIG. 1 is a sectional view of a conventional transflective LCD.
Referring to FIG. 1, a conventional transflective LCD 100 has a thin film transistor (TFT) array panel 160 having a plurality of TFTs, a color filter array panel 170 facing the TFT array panel 160 and having a plurality of color filters 150 and a common electrode 173, and a liquid crystal layer 180 interposed between the two panels 160 and 170.
The TFT array panel 160 has a first insulating substrate 110, a plurality of TFTs 120, a plurality of pixel electrodes 140 composed of transparent electrodes 141 and reflective electrodes 142 and connected to the TFTs 120, and an organic insulating layer 130 interposed between the TFTs 120 and the pixel electrodes 140. Each TFT 120 includes a gate electrode 121, a source electrode 123 and a drain electrode 124.
The area of each pixel electrode 140 is classified as a reflection region B where the reflective electrode 142 is disposed, and a transmission region A where the transparent electrode 141 is disposed.
The color filter array panel 170 has a second insulating substrate 171, a plurality of color filters 150 formed on the second substrate 171, and a common electrode 173 covering the color filters 150.
Such a transflective LCD has two different modes of operation: a transmission mode and a reflection mode. In the reflection mode, images are displayed by using external light L1 that is introduced through the color filter array panel 170 and is reflected back at the reflective electrode 142. In the transmission mode, images are displayed by using a back light (L2) that comes from a back light unit disposed on the back side of the TFT array panel 160 and passes out of the TFT array panel 160, the liquid crystal layer 180, and the color filter array panel 170.
In the reflection mode, the external light L1 passes through the color filter 150 twice to display an image, but in the transmission mode, the back light L2 passes through the color filter 150 just once to display an image. Accordingly, a difference in color reproduction is induced between the two modes.
Furthermore, in the reflection mode, the external light (L1) passes through the liquid crystal layer 180 twice so the length of light passage in the liquid crystal layer 180 is 2d. However, in the transmission mode, the back light L2 passes through the liquid crystal layer 180 just once so the length of light passage in the liquid crystal layer 180 is d. Such a difference of light passage length induces a difference of optical characteristics between the two modes.